1. Technical Field
The invention relates to the field of air seals, and more particularly to an air seal and retention system between an equipment housing and a removable module to deliver cooling air across or through electrical components mounted with the removable module.
2. Background Art
High power dissipating electronic assemblies require cooling air to be directed through a compact heat exchanger. This usually consists of a pair of printed circuit boards which may be bonded, or more likely fastened together by means of a frame positioned between the two modules. It is necessary to provide a reliable seal at each end of these modules to prevent leakage of any cooling air between the electronics rack and the removable module. Such leakage can have drastic effect on the system's thermal performance and overall reliability.
It is desirable to have an air seal between an electronics rack and the removable electronics module that also provides a means to ensure low deflections during vibration through use of a fixed boundary condition. It is also desirable to have a sealing system which is resistant to jamming and misalignment and conducive to maintenance and repair. It is further preferred to have a sliding air seal which is cost effective and resistant to corrosive environmental conditions.
Known systems for air cooling of removable electronic units use an elastomeric seal which is vulcanized into a channel shaped guide. This has proven to be a difficult method to manufacture the seal. The present invention vulcanizes the resilient seal to a flat, tapered surface which reduces cost, tooling, and manufacturing complexity.
Known systems for air cooling of removable electronic units also use silicone as the material for the seals which are damaged by exposure to solvents and petro-chemical agents. The new invention uses a double layer of fluorosilicone material or other environmentally resistant material having two durometer values with one on top of the other, and enclosing the slotted opening that is coated with a low friction material on the upper elastomeric material to facilitate low sliding friction when an electronics module having a tapered surface is slid over and compresses the seal.
The known systems for air cooling of removable electronic units utilize difficult to manufacture airseals that are difficult to field replace and are not resistant to chemical environments. The seal of the present invention also has a novel retention method that uses a tab on the bottom (m) and only requires one fastener at the top allowing the seal to be easily field replaceable.
Historically, all airborne radar systems have used classic multiple stage vibration isolation systems to minimize undesirable motion to meet phase noise performance requirements, e.g., 3 stages for AWACS, APG-68, and B1-B. It has been shown that excessive motion during vibration has been determined to be the root cause of phase noise problems in legacy radar systems.
Advances in electronic component technology has resulted in stiffer, higher frequency module structures. (Stiffer means less displacement for a given input.) The development of a wedgelock for use on RF modules was launched in the early 1980's. Wedgelock technology has been part of the solution to high vibration environments and has been used successfully to restrain RF modules on all programs commencing with the APG-68 and B1-B radar systems.
Such sealing methods for printed circuit modules cooled by a flow of air include, for example, U.S. Pat. No. 4,375,290, issued Mar. 1, 1983 to Alfred A. Zucchi et al. Other examples for background purposes are U.S. Pat. Nos. 2,843,806, 3,956,673, 4,006,388, and 4,277,815.
While the above cited references introduce and disclose a number of noteworthy advances and technological improvements within the art, none completely fulfills the specific objectives achieved by this invention.